The invention relates to a circular knitting machine for the production of plush fabrics which have a ground knit produced from ground threads and plush threads tied into said ground knit and comprising a needle cylinder with knitting needles intended for stitch formation, a sinker ring with sinkers intended for the formation of plush-thread loops, and a plurality of knitting systems, each with a means for controlling the knitting needles into a knock-over position after the pick-up of ground and/or plush thread.
Numerous embodiments of circular knitting machines for the production of plush fabrics are known. They have, as a rule, a needle cylinder provided with knitting needles and a sinker ring provided with sinkers. The plush fabrics obtained by them consist of what may be referred to as a ground knit, which is usually a fabric produced with a special ground thread and by the right/left or plain type of knitting, and of plush threads tied into the ground knit.
In plush fabrics of this type, pattern effects may be achieved, in particular, in that differently coloured plush threads are used or the plush threads are processed into plush loops of different length. The patternings mentioned first are designated as coloured patternings and the others as structural patternings.
To achieve coloured patterns, for example, circular knitting machines of the generic type designated in the introduction are known (DE 31 45 307 A1), in which first a ground thread and then, according to the pattern, one of a plurality of differently coloured plush threads can be inserted into all the knitting needles accommodated in the needle cylinder.
A particularly full and dense plush fabric is thereby obtained. A particular feature which, as a rule, is undesirable in coloured patternings of this type is due to the fact that floats occur wherever the plush threads are not inserted into the knitting needles. If floats of this kind extend over more than a few stitch wales, they disturb the visual appearance of the fabric. They are therefore eliminated by means of a shearing operation carried out after the knitting operation, the result of this, moreover, being that the plush loops formed are automatically cut open. The same applies correspondingly when plush fabrics having coloured patterns are produced by the plush threads being tied in partial rows into the ground knit, that is to say when in each stitch row, according to the pattern, only plush threads of a single colour are processed into stitches and laid in a floating manner therebetween, so that less full and dense plush surfaces are obtained. Consequently, all the plush fabrics described have, as a rule, what may be referred to as a velours surface, that is to say, when this knitting technique is employed, it is not possible to produce plush fabrics which have terry cloth surfaces provided with uncut plush loops.
One advantage of the type of knitting described is that it can also be used for the production of structural or high/low patterns. For this purpose, floats are formed in selected regions of a knit by means of all the plush threads which occur, so that, after the shearing operation, only the ground knit remains in these regions and is visually apparent (DE 39 27 815 A1, DE 197 07 053 A1). The formation of floats is in this case the equivalent to formation of loop-free zones or to a selection xe2x80x9cno plush loopsxe2x80x9d. The plush fabrics produced in this way, moreover, may be provided to a restricted extent with a coloured or knitted pattern by means of the additional insertion of float threads or further ground threads.
Coloured and structural patternings may, in principle, also be produced by means of other known circular knitting machines of the generic type designated in the introduction. For example, it is known (U.S. Pat. No. 2,710,527) to feed ground threads only to those knitting needles into which a plush thread is also inserted according to the pattern such that coloured patternings can be produced, in principle, only with the aid of partial rows. In plush fabrics produced in this way, therefore, the ground threads also float in the regions free of plush threads, in addition to the plush threads, which, on the one hand, may lead to a visually ugly appearance and to undesirable material properties and, on the other hand, entails the risk that, during the shearing operation, the ground-thread floats are also removed together with the plush-thread floats. To avoid this disadvantage, circular knitting machines are known (DE 30 24 705 A1) which serve the purpose oft when relatively long ground-thread floats occur, of controlling some selected needles into a knitting or tucking position, in order thereby to process the ground thread in the region of the floats partially into a stitch or to anchor it as a tuck stitch in the ground knit. Since the floating ground thread is tied into the ground knit at only a few points, there is at the same time the advantage that the number of tie-in points is kept low and no ugly bare gaps occur during the production of coloured patternings by means of partial rows. In addition, although it is also possible to provide comparatively wide regions in the plush fabric which have no plush loops at all, nevertheless, in this type of knitting, the main preoccupation is always to avoid long ground-fabric floats in regions having plush loops.
The circular knitting machines described hitherto are therefore all used, in particular, for the production of plush fabrics with coloured patternings. Existing pattern devices for the independent individual selection of knitting needles serve in this case merely for the purpose of separating those knitting needles which are to pick up a plush thread from the remaining knitting needles. By contrast, for all other patternings, in particular for high/low patterns in plush-thread regions or for knitted patterns in ground-thread regions, only cam parts are available which act on pattern butts, assigned to them, on knitting needles or on jacks assigned to these, so that the patterning possibilities are in this respect highly limited. This would in no way be changed even by the use of interchangeable cam parts which allow patternings, such as, for example, 1:1 tuck/float or 1:1 knit/float, and which are exchanged, as required.
A hitherto unavoidable problem of the circular knitting machines described is that the selection xe2x80x9cno plush loopsxe2x80x9d is possible only by the production of floats and the subsequent elimination of the floats by shearing. Consequently, knitted fabrics produced on these circular knitting machines, in so far as they are provided with structural patterns, always contain regions with stitches formed from ground and plush threads and regions with stitches formed solely from ground threads. In this case, in the regions free of plush threads, it is only the ground threads which determine the appearance of the plush fabric.
To avoid these properties which are not always desirable, circular knitting machines are known (U.S. Pat. No. 1,790,832, GB 1,104,859) which have pattern devices for selecting the sinkers and partially also additional pattern devices for selecting the knitting needles picking up the plush threads. The sinkers can in this case be controlled, according to the pattern, at least into a first position, in which plush loops are formed by means of a lower-lying sinker edge, or into a second position, in which plush loops are formed by means of a higher-lying sinker edge. The lower-lying sinker edges usually correspond in this case to those with which the ground-thread stitches are produced or looped. The plush loops produced by means of the lower sinker edges may in these cases also be designated as xe2x80x9cneutral loopsxe2x80x9d or no loopsxe2x80x9d. By these are meant, within the scope of the present invention, plush-thread loops which have essentially the same length as the ground-thread loops or legs and therefore, in the finished knit, lead to double stitches consisting of ground and plush threads, but do not appear as plush loops projecting beyond the ground knit. This affords the advantage that the selection xe2x80x9cno plush-thread loopsxe2x80x9d can be implemented by controlling the sinkers into the position intended for forming the shorter loops or the xe2x80x9cneutral loopsxe2x80x9d and the plush threads are processed in the regions free of plush loops, in the same way as the ground threads, so as to obtain smooth right/left or plain surfaces which, with correct plating, have the colour of the respective plush thread. The properties of the zones free of plush threads are therefore determined predominantly here by the plush threads, this being advantageous in some patternings.
Circular knitting machines of this type, set up mainly for the production of plush fabrics with structural patterns, have the disadvantage that, in practice, no coloured patternings can be produced and, despite the use of pattern devices in the form of pattern wheels or the like, the possibilities of structural patterning are limited. Moreover, the knitting needles can be controlled only selectively into one of two positions provided (knitting and non-knitting position), so that the ground knit can be provided at most with simple float/stitch patterns. The same applies, in principle, to circular knitting machines likewise already known, in which the sinkers can not only be brought into three positions, in order to form middle, high or no plush loops according to the pattern, but to which are also assigned interchangeable cam parts, in order to allow patternings selectively in the knit/float, knit/tuck or tuck/float types of knitting.
Finally, circular knitting machines are known (EP 0 629 727 B1), which are to make it possible to have both coloured patternings by the selection of the knitting needles according to a pattern and structural patternings by the selection of the sinkers according to a pattern, in order thereby to produce a plush knit which, in the same stitch row, possesses not only differently coloured plush loops, but also plush loops of different height. If, in a subsequent shearing operation, only the long plush loops are cut open and the plush-thread floats formed on the high sinker edges are removed, plush knits will then be obtained which have velours-like surfaces with high cut plush loops and terry-like surfaces with uncut plush loops of lesser height. It must be doubted, however, that this known method actually functions, since, for example, it is not clear how, with one and the same sinker control and in the same knitting system, differently coloured plush threads can be processed selectively into long or short plush loops and/or how floats are to be treated which are laid via sinker edges provided for short plus-thread loops. Moreover, such a circular knitting machine does not readily provide regions in a knitted fabric which are completely free of plush loops.
In view of the above it is a main object of this invention to design a knitting machine for the production of plush fabrics in such a manner that impoved patterning is possible.
A further object of this invention is to design a knitting machine for the production of plush fabrics in such a manner, that various knitted, colored and structural patterns can be produced.
Yet a further object is to provide plush fabrics having regions with plush threads and ground threads and regions only with ground thread by using one and the same knitting machine without a need for changing cam parts.
A further object underlying this invention is to design the circular knitting machine described above such that plush fabrics can be produced with various patterns both in fabric regions comprising plush threads and ground thread as well as in regions only comprising ground thread.
Further, an important object of this invention is to design the circular knitting machine identified above in such a manner that plush fabrics having long and short plush loops can be produced and that that short plush loops can be made by using different techniques.
The invention solves these and other objects by suggesting a circular knitting machine substantially as described above and having knitting systems with means for controlling the knitting needles into a knock-over position after the pick-up of ground and/or plush thread, said machine being characterized in accordance with this invention in that each of these knitting systems has, at a point located in front of the means, in the knitting direction, a first pattern device, provided with a ground-thread guide, for selectively controlling the knitting needles into a knitting or tucking position intended for the pick-up of ground thread or a non-knitting position intended for the non-pick-up of ground thread, a second pattern device, provided with a plush-thread guide, for selectively controlling the knitting needles into a pick-up position intended for the pick-up of plush thread or an intermediate position intended for the non-pick-up of plush thread, and a third pattern device for selectively controlling the sinkers at least into a first position intended for the formation of shorter plush-thread loops or a second position intended for the formation of longer plush-thread loops.
The invention for the first time affords the possibility of fully utilizing the advantages of patterning by needle control and the advantages of patterning by sinker control in one and the same circular knitting machines for the production of plush fabrics. It is thereby possible, in particular, to combine, virtually as desired, coloured and/or structural and/or knitted patterns in plush fabrics which have regions provided with plush loops and regions free of plush loops. If, according to a particularly preferred exemplary embodiment of the invention, the shorter plush-thread loops are formed via the same sinker edges as the ground-thread stitches, it is possible, moreover, to produce regions free of plush loops selectively by the formation of plush-thread floats or a subsequent shearing operation or by controlling the sinkers into the position provided for forming the shorter or neutral plush-thread loops. As a result, the visal impression of a ground-fabric portion located between two plush regions can be determined selectively by the coloured and/or knitted pattern of the ground thread or by the coloured and/or knitted pattern of the xe2x80x9cneutral sinker loopsxe2x80x9d covering the round threads, with the result that numerous new patternings are possible. The fact that, on each knitting system, only a single plush thread can be fed and the production of partial rows is therefore necessary for coloured patternings does not constitute an appreciable disadvantage in view of the multiple patterning possibilities.
Further advantageous features of the invention may be gathered from the subclaims.